The present invention generally relates to a brake fluid pressure generating apparatus. More particularly, the apparatus is applied to a mobile that is equipped with the brake fluid circuit.
In general, a vehicle brake system includes a brake booster and master cylinder to deliver a pressurized brake fluid to each wheel cylinder. The brake booster boosts the depression force to a brake pedal and outputs boosted force which is response to the depression of a brake pedal. The master cylinder converts the boosted force into a brake fluid pressure.
The engine vacuum tends to drop in the latest vehicle compared with the previous vehicle, on account of this reason a sufficient and/or stable boosted force is not generated utilizing a brake booster. To overcome the above-mentioned disadvantage, a pressure device which is used for traction control system is utilized for the brake system. In other words, a brake fluid in a reservoir tank is pressurized using the pressure device and then the pressurized brake fluid is supplied straight to each wheel cylinder.
The brake fluid amount in a master cylinder is increased by using supplemental pressure device and an excess amount of the brake fluid is existing in the brake fluid circuit. Therefore, when the brake pedal is released, the excesses amount of the brake fluid flows back to the master cylinder. The excess brake fluid operates a master cylinder piston from the initial position to unusual position. This movement damages seal materials in the master cylinder in which produces a fluid tight manner. Consequently, when the supplemental pressure device is utilized in the brake fluid circuit, a solid designed master cylinder seal structure is required. This will be a cause of a cost increase for the device.
A third pressure room is applied to the master cylinder to avoid supplemental pressure device disadvantage. In this construction, a brake fluid is supplied to the brake fluid independent of the primary brake fluid circuit. However, providing the third pressure room in the master cylinder complicates the structure of the master cylinder. Further, the third pressure room lengthens the size of the master cylinder.
The object of the present invention is to provide a brake fluid pressure generating apparatus which has a third pressure room with a simple structure and shortens the length of the master cylinder.
To achieve the subject matter of the present invention, a brake fluid pressure generating device composed of a brake booster which boosts the depression force to a brake pedal, a master cylinder that generates brake fluid pressure in response to the depression of the brake pedal using a master cylinder piston, a pressurized media introduction room defined between the brake booster and a master cylinder piston that operates the master cylinder independently of the brake booster and the master cylinder piston slides over a plurality of seal cups that are arranged on the master cylinder.
According to the invention, a brake fluid pressure regulation valve which is disposed between a reservoir tank and the pressurised media introduction room regulates the brake fluid d pressure from the pressurised media introduction room to the reservoir tank. This arrangement provides an appropriate brake fluid pressure to the wheel cylinders independently of the depressing of the brake pedal.
According to a further feature of the invention, the brake fluid pressure regulation valve has a cut off function that isolates the pressurised media introduction room from said reservoir tank. This specific arrangement provides substitutive function for a parking brake.
According to a further feature of the invention, the master cylinder piston is divided into two pieces and a cross section of the first master cylinder piston is relatively bigger than a cross section of the second master cylinder piston. This construction provides large pressurized brake fluid receiving section on the first master cylinder piston and minimizes a brake fluid pressure in the pressurised media introduction room to slide the first master cylinder piston.